Piezoelectric crystal mounting



March 7 1944'. R. BECHMANN ET AL 2,343,738.

rmzumrnxc CRYSTAL MOUNTING Filed July 19, 1941 INVENTQRS Zfi gezjzrgiznem ATTORNEY Patented Mar. 7, 194 v UNITED STATES PATENT, OFFICE IPIEZOELECTRIC CRYSTAL MOUNTING Rudolf Bechmann, Heinz E. Kundt, andHeinrich Bremer, Berlin, Germany; vested in the Alien Property CustodianApplication July 19, 1941, Serial No. 403,096

In Germany April 2, 1940 9 Claims. (Cl. 171-327) This invention relatesto a new and useful sup- Fig. 3 is an end view of a portion of the clampporting or mounting means for long-wave piezofor the stem, and electriccrystals. Fig. 4 is a perspective view of a complete An object of thisinvention is to provide imcrystal holder employing the principles andteaproved mounting or holding apparatus for long- 5 tures of thisinvention. wave piezo-electric crystals wherein damping ef- Referringnow to the accompanying drawing, fects are minimized. Fig. 1 illustratesa pestle, stem or stud S which is Heretofore in the mounting oflong-wave soldered to the quartz plate or crystal Q or to a crystals, ithas been suggested to suitably metalmetallized surface thereof servingas an electrode. lize the two-major surfaces of a piezo-electric in Onthe stem S, for afinite length, there arises a crysta and then mount asingle rigid metal stem standing wave h ngnodes at points indicated toone lot the major surfaces for supporting the by K and loops oranti-nodes at points marked crystal The assembly of crystal, electrodeand B- This standing wave is set up y hi kness Stem ls ln turnsupportedby suitable means sevibrations of the crystal even though the same curedto the stem. such apparatus is dis los d i5 is operating in or alonganother dimension. If, in the Bremer et al. Patent 2,310,612, issued estem 3 is supported at n p c for in- February 9, .1943. This patent,describes the stance, which happens to lie in the vicinity of solderingof a crystal plate-to a rigid metal stem a l p. e pp t or m u n eans Swill also at a nodal point on the crystal, The st forms be excited toexperience vibrations inasmuch as the support for th crystal. This eth dnd 20 the crystal holder or mounting system is by its apparatusliorsupporting crystals are best suited construction in fixed couplingrelation with the for low frequency contour crystals which are crystal.This entails incidental frequency changes excited. ,lso' as to undergolongitudinal vibrations and a rise in the damping of the Vibrating yalong rigiajor dimension Th t l period of tern, as compared with afreely vibrating crystal. such oscillations or vibrations is governed,as a 25 This action, as has been ascertained experimenpractical'matter,by the diameter of the crystal, tally. arise n on in the case Olongitudinally if circular, or the length of a side or'edge, ifvibrating cry Where echanical couplin rectangular or square. with theholder results from the longitudinal 1 Hence, it would appear that thesenatural transversal contraction coeillcient of the crystal,

longitudinal vibrations are dependent only upo but also arises withtransversal vibrations of the i the dimensions of the crystal plane orelectrode crystal in Which Case the Crystalline p a 8 surfac and notupon the thicknes f the crystal hibit also a certaininteractioncoeflicient, that is, plates. However, it will be found that oscillathecross Shearing cqvemclemtions of small amplitude do arise in thethickness W, or g toxthe pr invention, the direction ofthe crystal andthese are due to comdisadvantage of reduced amplitude of desired plexcouplings within the crystal element or oscillations caused by thedamping eiIect of the plate. The thickness oscillations are propagatedsupport mine crystal and other dlmcumes here along the Supporting stemor stud and cause inbefore described are overcome by supporting orundesirable damping of the crystal. To overholding the stem 8 at p mintK the come-such damping a further object of this on standing wavearising alongthe stem. It will be invention and it is effected, as willbe explained found expedient m this to make the in greater detailhereinafter by supporting the range or dimension of the clamp requiredfor stem at a selected point which will permit free 23:21: 1 z f f gziig gggs 2' ai s: 3:5 :32 of the crystal with minimum of 1garded asvery small compared with a half wave- This invention will be furtherdescribed with :25;;: 1;xgfi zg g gg figgfgigh basic reference to theaccompanying drawing in which: idea underlying this invention is shownin Fig 2 1 is a perspective View of a crystal to which of the appendeddrawing where the stern S has a is fasteneda supporting Stu Stem- Thecurve 61 cylindrical extension A which is located at a drawn 0 e Stemrepresents a Standing Wave nodal point of the standing wave developed onSet p thereon y thickness Oscillations 0f the the stem. The distance dbetween crystal plate crystal. Q and the portion of enlarged diameter orcross- Fig. 2 is a side elevation of a crystal, supportpiece A istherefore roughly one quarter or three ing stem and clamp for the stem.56 quarters of a wavelength. More generally the distance d is made anodd multiple of a quarter wavelength, the wavelength taken being that ofthe standing wave set up upon the stem S. In this way the reaction ofsuch a holder or mounting system turns out to be particularly smallespecially where the cylindrical extension A, as shown in Fig. 3, islaterally clamped in. For instance, the extension A of stem S is clampedor tensionally held between two sheets or laminae B which are pressedtogether by the screws Sch. An exemplified embodiment of a completelymounted crystal along the line of the above disclosure in shown in Fig.4. The support T which bears the stem with a cylindrical extension pieceis secured upon a base plate G. The electrical connection to one of thetwo metallized surfaces of the crystal is established through the saidsupport '1 and the stem 8.: Connection to the other metallized crystalelectrode surface is made, for example, through a" supply lead wire Z,and a slender wire D which is soldered fast to a metal surface oncrystal Q and to the connecting wire Z.

What is claimed is 1. A piezo-electric crystal holder comprising acrystal plate, a rigid stem secured to one face of said crystal plateand means located at a nodal point of vibration on said stem forsupporting said crystal in an operative position to provide improvedoperation.

2. A piezo-electric crystal holder comprising a crystal plate, a rigidstem secured to one face of said crystal plate and a cylindricalextension member located at a nodal point of vibration on said stem forsupporting said crystal in an operative position to provide improvedoperation.

3. A piezo-electric crystal holder comprising a crystal plate, a rigidstem secured to one face of said crystal plate and a cylindricalextension member located at a nodal point of vibration on said stem,.asupporting sheet having means for engaging said cylindrical extensionmember for supporting said crystal in an operative position to provideimproved operation.

4. A piezo-electric crystal holder comprising a crystal plate, a rigidstem secured to one face of said crystal plate, a wire secured to theother face of said crystal plate, and means located at a nodal point ofvibration on said stern for supporting said crystal in an operativeposition to provide improved operation.

5. A piezo-electric crystal holder comprising a crystal plate, a rigidstem secured to one face of said crystal plate, a wire secured to theother face of said crystal plate, and means located at a point on saidstem, which point is approximately an odd multiple of one-quarter wavelength to which the crystal is normally responsive distant from saidcrystal, said means being provided for supporting said crystal in anoperative position to provide improved operation.

6. A piezo-electric crystal holder comprising a crystal plate having twometallized surfaces, a rigid stem secured to one of said metallizedsurfaces, a wire secured to the other metallized surface of saidcrystal, and supporting means located at a point on said stem, saidpoint being removed from said crystal at a distance which isapproximately an odd multiple of a quarter wave length to which thecrystal is normally respon- .sive.

7. Piezo-electric apparatus comprising a crystal plate, a rigid stemphysically secured to one of the surfaces of said crystal, said stemacting as a support for the crystal plate and being mechanicallyvibrated by vibrations of said crystal whereby a mechanical standingwave is set up on said stem, instrumentalities for clamping andsupporting said stem at a nodal point of mechanical vibration on saidstem, and means for establishing electrical connection with a pair ofelectrode faces of said crystal plate.

8. Piezo-electric apparatus comprising a crystal plate, a rigid stemphysically secured to one of the electrode faces of said crystal, saidstem acting as a support for the crystal plate and being vibrated bymechanical vibrations of said crystal whereby a standing mechanical waveis set up on said stem, apparatus for clamping and supporting said stemat a point substantially an odd multiple of a quarter wavelength of saidmechanical wave away from said surface to which said stem is secured,and means including said stem for establishing electrical connectionwith the electrode surfaces of said crystal plate.

9. Apparatus as claimed in the preceding claim characterized by the factthat the clamping means for said stem extend along the stem for adistance which is small relative to a quarter wavelength of the standingmechanical wave.

RUDOLF BECHMANN. HEINRICH BREMER. HEINZ E. KUNDT.

